ACL injury

Tearing of the anterior cruciate ligament (ACL) is a very common sporting injury. Many people hear or feel a “pop” in the knee when an ACL injury occurs. Your knee may swell, feel unstable and become too painful to bear weight. ACL injuries most commonly occur during sports that involve sudden stops, jumping or changes in direction — such as basketball, soccer, football, tennis, downhill skiing, volleyball and gymnastics.

Ligaments are strong bands of tissue that attach one bone to another bone. The anterior cruciate ligament is one of two ligaments that crosses the middle of your knee that connects your thighbone (femur) to your shinbone (tibia) and helps stabilize your knee joint (Figures 1 and 2). The anterior cruciate ligament (ACL) limits hyperextension of the knee (which normally does not occur at this joint) and prevents the anterior sliding of the tibia on the femur. When the anterior cruciate ligament is damaged, there is usually a partial or complete tear of the ligament. A mild ACL tear may stretch the ligament but leave it intact. Many people hear or feel a “pop” in the knee when an anterior cruciate ligament injury occurs. Your knee may swell, feel unstable, may feel like it gives way and become too painful to bear weight.

Anterior cruciate ligament (ACL) injuries have an incidence of approximately 252,000 yearly ¹. Approximately half of anterior cruciate ligament injuries occur in combination with damage to the meniscus, articular cartilage, or other ligaments. Additionally, patients may have bruises of the bone beneath the cartilage surface. These may be seen on a magnetic resonance imaging (MRI) scan and may indicate injury to the overlying articular cartilage. Persons who experience anterior cruciate ligament injuries have an increased risk of arthritis.

Women are two to eight times more likely to have an anterior cruciate ligament injury than similarly trained men ², ³, ⁴, ⁵, ⁶. It has been proposed that this is due to differences in physical conditioning, muscular strength, and neuromuscular control. Other hypothesized causes of this gender-related difference in anterior cruciate ligament injury rates include pelvis and lower extremity (leg) alignment, increased ligamentous laxity, and the effects of estrogen on ligament properties.

An anterior cruciate ligament tear can happen when you change direction rapidly, slow down when running, land after a jump, or receive a direct blow to your knee. Athletes who participate in high demand sports like soccer, skiing and basketball are sports where anterior cruciate ligament knee injuries can happen.

Injuries to the posterior cruciate ligament (PCL) are less common. It can be injured during a direct blow to the tibia when the knee is bent, or when the knee is over-straightened.

The patient with an anterior cruciate ligament injury should be referred to the orthopedic surgeon to discuss treatment options and a physical therapist (PT) for rehabilitation.

Depending on the severity of your anterior cruciate ligament injury and your activity level, treatment may include rest and rehabilitation exercises to help you regain strength and stability or surgery to replace the torn ligament followed by rehabilitation. A proper training program may help reduce the risk of an anterior cruciate ligament injury.

To treat the immediate ACL injury:

• Use R.I.C.E. model of self-care at home (rest, ice, compression, elevation)
• Take pain relievers such as ibuprofen as needed
• You can use an elastic bandage around your knee
• Use a splint or walk with crutches if needed

ACL injuries, depending upon their severity, can be managed nonoperatively or operatively.

Nonoperative treatment is typically reserved for those with low functional demands, type and severity of ACL tear, time of injury, and subsequent assessment. Continued monitoring and treatment by an orthopedic surgeon and physical therapist is necessary and will improve your functional status and stability post-injury. Of note, about half of the patients who initially choose the non-operative pathway will later choose to undergo surgical repair.

The decision to undergo operative treatment is based upon many factors such as the patient’s baseline level of physical activity, functional demands, age, occupation, and other associated injuries, if present ⁷. Athletes and individuals who are younger and more active tend to opt for surgical repair and reconstruction. Other surgical repair/reconstruction candidates are those with significant instability of the knee and/or multiple knee structures injured. Operative treatment is typical with a tissue graft. In a recent systematic review, 81% of those involved treated with ACL reconstruction returned to some athletic activity, 65% returned to the preinjury level of competition, and 55% of high-level athletes returned to normal play and competition. Although, it has been reported that of those who undergo surgical repair, overall 90% return to near-normal functioning. The factors that may contribute to a lower percentage of return to play may be secondary to external factors such as fear of reinjury.

Your doctor may recommend surgery if:

• You’re an athlete and want to continue in your sport, especially if the sport involves jumping, cutting or pivoting
• More than one ligament or the fibrous cartilage in your knee also is injured
• The injury is causing your knee to buckle during everyday activities

During ACL reconstruction, the surgeon removes the damaged ligament and replaces it with a segment of tendon — tissue similar to a ligament that connects muscle to bone. This replacement tissue is called a graft.

Your surgeon will use a piece of tendon from another part of your knee or a tendon from a deceased donor.

After surgery you’ll resume another course of rehabilitative therapy. Successful ACL reconstruction paired with rigorous rehabilitation can usually restore stability and function to your knee.

There’s no set time frame for athletes to return to play. Recent research indicates that up to one-third of athletes sustain another tear in the same or opposite knee within two years. A longer recovery period may reduce the risk of re-injury.

In general, it takes as long as a year or more before athletes can safely return to play. Doctors and physical therapists will perform tests to gauge your knee’s stability, strength, function and readiness to return to sports activities at various intervals during your rehabilitation. It’s important to ensure that strength, stability and movement patterns are optimized before you return to an activity with a risk of ACL injury.

Types of ACL tears

About half of all injuries to the anterior cruciate ligament occur along with damage to other structures in the knee, such as articular cartilage, meniscus, or other ligaments.

Injured ligaments are considered “sprains” and are graded on a severity scale.

• Grade 1 Sprains. The ligament is mildly damaged in a Grade 1 Sprain. It has been slightly stretched, but is still able to help keep the knee joint stable.
• Grade 2 Sprains. A Grade 2 Sprain stretches the ligament to the point where it becomes loose. This is often referred to as a partial tear of the ligament.
• Grade 3 Sprains. This type of sprain is most commonly referred to as a complete tear of the ligament. The ligament has been split into two pieces, and the knee joint is unstable.

Partial tears of the anterior cruciate ligament are rare; most ACL injuries are complete or near complete tears.

Complications of ACL injury

A short term complication is that you will need to take it easy until your injured ligament has healed.

Other complications may include:

• Torn meniscus: As the ACL and meniscus are both structures in your knee which are quite close, if you injure one you may have injured the other. An injured meniscus can increase the risk of joint problems later on, however, evidence thus far has not yet supported meniscus repairs to minimize or delay the rate of osteoarthritis ⁸, ⁹, ¹⁰.
• Arthritis: People who experience an ACL injury have a higher risk of developing osteoarthritis in the knee. This is when your joint cartilage gets rough over time leaving it deficient. Osteoarthritis may occur even if you have surgery to reconstruct the anterior cruciate ligament. This is a very common complication that arises as a long term complication. About half the people with an ACL tear develop osteoarthritis in the involved joint 10 to 20 years later. Multiple factors likely influence the risk of arthritis, such as the severity of the original injury, the presence of related injuries in the knee joint or the level of activity after treatment.

The Knee Joint

Three bones meet to form your knee joint: your thighbone (femur), shinbone (tibia), and kneecap (patella). Your kneecap sits in front of the joint to provide some protection.

The knee joint (tibiofemoral joint) is the largest and most complex joint of the body (Figures 1) and its evaluation can present a challenge. It is a modified hinge joint (because its primary movement is a uniaxial hinge movement) that consists of three joints within a single synovial cavity:

1. Laterally is a tibiofemoral joint, between the lateral condyle of the femur, lateral meniscus, and lateral condyle of the tibia, which is the weight-bearing bone of the leg.
2. Medially is another tibiofemoral joint, between the medial condyle of the femur, medial meniscus, and medial condyle of the tibia.
3. An intermediate patellofemoral joint is between the patella and the patellar surface of the femur.

Bones are connected to other bones by ligaments. There are four primary ligaments in your knee. The major ligaments of the knee are the anterior cruciate ligament (ACL), the posterior cruciate ligament (PCL), and the medial collateral ligament (MCL) and lateral collateral ligament (LCL). They act like strong ropes to hold the bones together and keep your knee stable. The major ligaments of the knee, along with the muscles acting on the knee, provide the joint’s stability.

Knee Joint Anatomical Components

• Articular capsule. Independent capsule unites the bones of the knee joint. The ligamentous sheath surrounding the kneww joint consists mostly of muscle tendons or their expansions. There are, however, some capsular fibers connecting the articulating bones.
• Medial and lateral patellar retinacula. Fused tendons of insertion of the quadriceps femoris muscle and the fascia lata (fascia of thigh) that strengthen the anterior surface of the joint.
• Patellar ligament. Continuation of common tendon of insertion of quadriceps femoris muscle that extends from the patella to the tibial tuberosity. Also strengthens the anterior surface of the joint. Posterior surface of the ligament is separated from the synovial membrane of the joint by an infrapatellar fat pad.
• Oblique popliteal ligament. Broad, flat ligament that extends from the intercondylar fossa and lateral condyle of the femur to the head and medial condyle of the tibia. The ligament strengthens the posterior surface of the joint.
• Arcuate popliteal ligament. Extends from lateral condyle of femur to styloid process of the head of the fibula. Strengthens the lower lateral part of the posterior surface of the joint.
• Tibial collateral ligament. Broad, flat ligament on the medial surface of the joint that extends from the medial condyle of the femur to the medial condyle of the tibia. Tendons of the sartorius, gracilis, and semitendinosus muscles, all of which strengthen the medial aspect of the joint, cross the ligament. The tibial collateral ligament is firmly attached to the medial meniscus.
• Fibular collateral ligament. Strong, rounded ligament on the lateral surface of the joint that extends from the lateral condyle of the femur to the lateral side of the head of the fibula. It strengthens the lateral aspect of the joint. The ligament is covered by the tendon of the biceps femoris muscle. The tendon of
  the popliteal muscle is deep to the ligament.
• Intracapsular ligaments. Ligaments within capsule connecting tibia and femur. The anterior and posterior cruciate ligaments are named based on their
  origins relative to the intercondylar area of the tibia. From their origins, they cross on their way to their destinations on the femur.
  • Anterior cruciate ligament (ACL). Extends posteriorly and laterally from a point anterior to the intercondylar area of the tibia to the posterior part of the medial surface of the lateral condyle of the femur. The Anterior cruciate ligament (ACL) limits hyperextension of the knee (which normally does not occur at this joint) and prevents the anterior sliding of the tibia on the femur. This ligament is stretched or torn in about 70% of all serious knee injuries.
  • Posterior cruciate ligament (PCL). Extends anteriorly and medially from a depression on the posterior intercondylar area of the tibia and lateral meniscus to the anterior part of the lateral surface of the medial condyle of the femur. The posterior cruciate ligament (PCL) prevents the posterior sliding of the tibia (and anterior sliding of the femur) when the knee is flexed. This is very important when walking down stairs or a steep incline.
• Articular discs (menisci). Two fibrocartilage discs between the tibial and femoral condyles help compensate for the irregular shapes of the bones and circulate synovial fluid.
  • Medial meniscus. Semicircular piece of fibrocartilage (C-shaped). Its anterior end is attached to the anterior intercondylar fossa of the tibia, anterior to the anterior cruciate ligament. Its posterior end is attached to the posterior intercondylar fossa of the tibia between the attachments of the posterior cruciate ligament and lateral meniscus.
  • Lateral meniscus. Nearly circular piece of fibrocartilage (approaches an incomplete O in shape). Its anterior end is attached anteriorly to the intercondylar eminence of the tibia, and laterally and posteriorly to the anterior cruciate ligament. Its posterior end is attached posteriorly to the intercondylar eminence of the tibia, and anteriorly to the posterior end of the medial meniscus. The anterior surfaces of the medial and lateral menisci are connected to each other by the transverse ligament of the knee and to the margins of the head of the tibia by the coronary ligaments.
• The more important bursae of the knee include the following:
  • Prepatellar bursa between the patella and skin.
  • Infrapatellar bursa between superior part of tibia and patellar ligament.
  • Suprapatellar bursa between inferior part of femur and deep surface of quadriceps femoris muscle.

Figure 1. Knee joint

Figure 2. Knee joint ligaments

Figure 3. Knee joint ligaments (posterior view)

ACL injury causes

Most ACL injuries happen during sports and fitness activities that can put stress on the knee:

• Changing direction rapidly
• Stopping suddenly
• Slowing down while running
• Landing from a jump incorrectly
• Direct contact or collision, such as a football tackle

An anterior cruciate ligament injury can occur if you:

• Get hit very hard on the side of your knee, such as during a football tackle
• Overextending your knee joint
• Quickly stop moving and change direction while running, landing from a jump, or turning

Several studies have shown that female athletes have a higher incidence of ACL injury than male athletes in certain sports. It has been proposed that this is due to differences in physical conditioning, muscular strength, and neuromuscular control. Other suggested causes include differences in pelvis and lower extremity (leg) alignment, increased looseness in ligaments, and the effects of estrogen on ligament properties.

Mechanism of anterior cruciate ligament injury

Patients who sustain anterior cruciate ligament injuries classically describe a popping sound, followed by immediate pain and swelling of the knee. The feeling of instability or giving-way episodes typically limit the ability to participate in activities. Patients might describe the feeling of instability with the “double fist sign” (i.e., fists facing each other, rotating in a grinding motion).

Anterior cruciate ligament injuries caused by contact require a fixed lower leg (i.e., when planted) and torque with enough force to cause a tear. Contact injuries account for only about 30 percent of anterior cruciate ligament injuries ¹¹. The remaining 70 percent of anterior cruciate ligament tears are noncontact injuries occurring primarily during deceleration of the lower extremity, with the quadriceps maximally contracted and the knee at or near full extension ¹², ¹³, ¹⁴. In noncontact scenarios, the stress on the anterior cruciate ligament resembles that of a collision of the knee. When the knee is at or near full extension, quadriceps contraction increases anterior cruciate ligament tensile force. The hamstrings, which stabilize the anterior cruciate ligament posteriorly, are often minimally contracted during these injuries, particularly if the hip is extended and the body weight is on the heel, allowing for excessive forward shifting of the femur on the tibia ¹⁵. Examples of this type of noncontact injury include skiers or snowboarders whose ankles are locked when they fall backward onto the snow; soccer players who execute sudden cutting maneuvers; or basketball players who land on an internally rotated knee without full flexion ¹⁶.

Risk factors for ACL injury

There are a number of factors that increase your risk of an ACL injury, including:

• Being female — possibly due to differences in anatomy, muscle strength and hormonal influences. Female athletes have been reported to sustain non-contact ACL injuries at a rate higher than their male counterparts. Recent studies indicate a 2 to 8 fold increase in females compared to similarly trained males ³, ⁴, ⁵, ⁶
• Participating in certain sports, such as soccer, football, basketball, gymnastics and downhill skiing
• Poor conditioning
• Using faulty movement patterns, such as moving the knees inward during a squat
• Wearing footwear that doesn’t fit properly ¹⁷
  
• Using poorly maintained sports equipment, such as ski bindings that aren’t adjusted properly
• Playing on artificial turf ¹⁸ 
  

Greatest predictors for anterior cruciate ligament injury include anterior knee laxity, increased body mass index (BMI) and family history ¹⁹. Additional factors may include biomechanical differences, increased posterior tibial slope, and hormones (with a greater proportion of injuries occurring in the follicular phase as compared to the luteal phase of the menstrual cycle) ²⁰, ²¹, ²².

Other risk factors for ACL injury include inclement weather, intercondylar notch stenosis, variations in sagittal condylar shape, increased tibial slope, increased posterior slope, and potential genetic influence ²³, ²⁴.

ACL injury prevention

Proper training and exercise can help reduce the risk of ACL injury. A physical therapist, athletic trainer or other specialist in sports medicine can provide assessment, instruction and feedback that can help you reduce risks. Programs to reduce ACL injury include:

• Exercises that strengthen leg muscles, particularly hamstring exercises, to ensure an overall balance in leg muscle strength
• Exercises to strengthen the core: hips, pelvis and lower abdomen
• Training and exercise for proper techniques and knee position in jumping and landing
• Training to improve techniques for pivoting and cutting

Gear

Wear footwear and padding that is appropriate for your sport to help prevent injury. If you downhill ski, make sure your ski bindings are adjusted correctly by a trained professional so that your skis will release appropriately when you fall.

Wearing a knee brace does not appear to prevent ACL injury or reduce the risk of recurring injury after surgery.

ACL knee injury symptoms

Signs and symptoms that you may notice at the time of ACL injury may include:

• A sudden “pop” sound or or a “popping” sensation in your knee
• Rapid swelling of the knee within minutes to hours of the injury. This is caused by bleeding into the knee
• Moderate to severe pain in your knee and inability to continue activity
• Loss of range of motion

Symptoms that may occur days to weeks after the ACL injury include:

• A feeling of instability or “giving way” with weight bearing: After the swelling improves you may feel a sense of ‘instability’ in the injured knee. This means the knee moves around too much and may lead to the knee giving way. This is often felt during activities such as squatting, walking down stairs, pivoting on the knee or stepping sideways.
• Ongoing knee pain
• Ongoing swelling (usually less severe than at the time of injury)

ACL injury diagnosis

During the physical exam, your doctor will check your knee for swelling and tenderness — comparing your injured knee to your uninjured knee. He or she also may move your knee into a variety of positions to assess range of motion and overall function of the joint.

Physical Examination and Patient History

During your first visit, your doctor will talk to you about your symptoms and medical history.

During the physical examination, your doctor will check all the structures of your injured knee, and compare them to your non-injured knee. Most ligament injuries can be diagnosed with a thorough physical examination of the knee.

In addition to performing special tests for identifying meniscus tears and injury to other ligaments of the knee, the physician will often perform the Lachman’s test to see if the ACL is intact.

If the ACL is torn, the examiner will feel increased forward (upward or anterior) movement of the tibia in relation to the femur (especially when compared to the normal leg) and a soft, mushy endpoint (because the ACL is torn) when this movement ends.

Lachman Test

Imaging Tests

Other tests which may help your doctor confirm your diagnosis include:

X-rays. Although they will not show any injury to your anterior cruciate ligament, x-rays can show whether the injury is associated with a broken bone.

Magnetic resonance imaging (MRI) scan. This study creates better images of soft tissues like the anterior cruciate ligament. However, an MRI is usually not required to make the diagnosis of a torn ACL.

ACL injury treatment

If you have suffered an ACL injury, treatment depends on many factors, including the severity, your lifestyle, work, sport and age. Right after an ACL injury, an ACL tear is treated with the “RICE” therapy, which includes rest, ice, compression of the affected knee (with an elastic bandage), and elevation of the affected knee. For pain relief, you may need over-the-counter pain medicine such as acetaminophen (Tylenol or store brand) or ibuprofen (Advil, Motrin, or store brand).

ACL injuries can be managed nonoperatively or surgically. The patient with an anterior cruciate ligament injury should be referred to the orthopedic surgeon to discuss treatment options and a physical therapist for rehabilitation.

Most partial tears can be treated with bracing and physical therapy (PT). A person might need to use crutches as the tear heals.

Some complete ACL tears need surgery. The need for surgery depends on many things, including:

• the type of the activities (or sports) the person wants to do
• if the person is an athlete
• age
• other injuries to the knee
• if the knee “gives way” or feels unstable

Your expectations for knee function or performance may play a role in determining whether ACL reconstruction is needed. With an ACL tear, your knee is usually unstable. This instability may cause your knee to “give way” or feel unstable which will significantly influence knee function. A course of physical therapy may successfully treat an ACL injury for people who are relatively inactive, engage in moderate exercise and recreational activities, or play sports that put less stress on the knees.

If physiotherapy and the possibly the use of a special ACL brace do not improve the stability of the joint, your doctor may recommend surgical reconstruction. Your Sports physician will also consider whether there are additional knee injuries which make surgery necessary, such as a meniscal tear and discuss fully your options of treatment.

Anterior cruciate ligament tear first-aid care

Prompt first-aid care can reduce pain and swelling immediately after an ACL injury to your knee. Follow the R.I.C.E. model of self-care at home:

• Rest. General rest is necessary for healing and limits weight bearing on your knee.
• Ice. When you’re awake, try to ice your knee at least every two hours for 20 minutes at a time.
• Compression. Wrap an elastic bandage or compression wrap around your knee.
• Elevation. Lie down with your knee propped up on pillows.

Natural history of ACL injury

What happens naturally with an ACL injury without surgical intervention varies from patient to patient and depends on the patient’s activity level, degree of injury and instability symptoms.

The prognosis for a partially torn ACL is often favorable, with the recovery and rehabilitation period usually at least 3 months. However, some patients with partial ACL tears may still have instability symptoms. Close clinical follow-up and a complete course of physical therapy helps identify those patients with unstable knees due to partial ACL tears.

Complete ACL ruptures have a much less favorable outcome without surgical intervention. After a complete ACL tear, some patients are unable to participate in cutting or pivoting-type sports, while others have instability during even normal activities, such as walking. There are some rare individuals who can participate in sports without any symptoms of instability. This variability is related to the severity of the original knee injury, as well as the physical demands of the patient.

About half of ACL injuries occur in combination with damage to the meniscus, articular cartilage or other ligaments. Secondary damage may occur in patients who have repeated episodes of instability due to ACL injury. With chronic instability, a large majority of patients will have meniscus damage when reassessed 10 or more years after the initial injury. Similarly, the prevalence of articular cartilage lesions increases in patients who have a 10-year-old ACL deficiency.

Nonsurgical Treatment

A torn ACL will not heal without surgery. But nonsurgical treatment may be effective for patients who are elderly or have a very low activity level. If the overall stability of the knee is intact, your doctor may recommend simple, nonsurgical options.

Bracing. Your doctor may recommend a brace to protect your knee from instability. To further protect your knee, you may be given crutches to keep you from putting weight on your leg.

Physical therapy. As the swelling goes down, a careful rehabilitation program is started. Specific exercises will restore function to your knee and strengthen the leg muscles that support it.

In nonsurgical treatment, progressive physical therapy and rehabilitation can restore the knee to a condition close to its pre-injury state and educate the patient on how to prevent instability. This may be supplemented with the use of a hinged knee brace. However, many people who choose not to have surgery may experience secondary injury to the knee due to repetitive instability episodes.

Surgical treatment is usually advised in dealing with combined injuries (ACL tears in combination with other injuries in the knee). However, deciding against surgery is reasonable for select patients.

Nonsurgical management of isolated ACL tears is likely to be successful or may be indicated in patients:

• With partial tears and no instability symptoms
• With complete tears and no symptoms of knee instability during low-demand sports who are willing to give up high-demand sports
• Who do light manual work or live sedentary lifestyles
• Whose growth plates are still open (children)

Surgical Treatment

ACL tears are not usually repaired using suture to sew it back together, because repaired ACLs have generally been shown to fail over time. Therefore, the torn ACL is generally replaced by a substitute graft made of tendon.

• Patellar tendon autograft (autograft comes from the patient)
• Hamstring tendon autograft
• Quadriceps tendon autograft
• Allograft (taken from a cadaver) patellar tendon, Achilles tendon, semitendinosus, gracilis, or posterior tibialis tendon

Patient Considerations

Active adult patients involved in sports or jobs that require pivoting, turning or hard-cutting as well as heavy manual work are encouraged to consider surgical treatment. This includes older patients who have previously been excluded from consideration for ACL surgery. Activity, not age, should determine if surgical intervention should be considered.

In young children or adolescents with ACL tears, early ACL reconstruction creates a possible risk of growth plate injury, leading to bone growth problems. The surgeon can delay ACL surgery until the child is closer to skeletal maturity or the surgeon may modify the ACL surgery technique to decrease the risk of growth plate injury.

A patient with a torn ACL and significant functional instability has a high risk of developing secondary knee damage and should therefore consider ACL reconstruction.

It is common to see ACL injuries combined with damage to the menisci, articular cartilage, collateral ligaments, joint capsule, or a combination of the above. The “unhappy triad,” frequently seen in football players and skiers, consists of injuries to the ACL, the MCL, and the medial meniscus.

In cases of combined injuries, surgical treatment may be warranted and generally produces better outcomes. As many as half of meniscus tears may be repairable and may heal better if the repair is done in combination with the ACL reconstruction.

Rebuilding the ligament. Most ACL tears cannot be sutured (stitched) back together. To surgically repair the ACL and restore knee stability, the ligament must be reconstructed. Your doctor will replace your torn ligament with a tissue graft. This graft acts as a scaffolding for a new ligament to grow on.

Patellar tendon autograft

The middle third of the patellar tendon of the patient, along with a bone plug from the shin and the kneecap is used in the patellar tendon autograft. Occasionally referred to by some surgeons as the “gold standard” for ACL reconstruction, it is often recommended for high-demand athletes and patients whose jobs do not require a significant amount of kneeling.

In studies comparing outcomes of patellar tendon and hamstring autograft ACL reconstruction, the rate of graft failure was lower in the patellar tendon group. In addition, most studies show equal or better outcomes in terms of postoperative tests for knee laxity (Lachman’s, anterior drawer and instrumented tests) when this graft is compared to others. However, patellar tendon autografts have a greater incidence of postoperative patellofemoral pain (pain behind the kneecap) complaints and other problems.

The pitfalls of the patellar tendon autograft are:

• Postoperative pain behind the kneecap
• Pain with kneeling
• Slightly increased risk of postoperative stiffness
• Low risk of patella fracture

Hamstring tendon autograft

The semitendinosus hamstring tendon on the inner side of the knee is used in creating the hamstring tendon autograft for ACL reconstruction. Some surgeons use an additional tendon, the gracilis, which is attached below the knee in the same area. This creates a two- or four-strand tendon graft. Hamstring graft proponents claim there are fewer problems associated with harvesting of the graft compared to the patellar tendon autograft including:

• Fewer problems with anterior knee pain or kneecap pain after surgery
• Less postoperative stiffness problems
• Smaller incision
• Faster recovery

The graft function may be limited by the strength and type of fixation in the bone tunnels, as the graft does not have bone plugs. There have been conflicting results in research studies as to whether hamstring grafts are slightly more susceptible to graft elongation (stretching), which may lead to increased laxity during objective testing. Recently, some studies have demonstrated decreased hamstring strength in patients after surgery.

There are some indications that patients who have intrinsic ligamentous laxity and knee hyperextension of 10 degrees or more may have increased risk of postoperative hamstring graft laxity on clinical exam. Therefore, some clinicians recommend the use of patellar tendon autografts in these hypermobile patients.

Additionally, since the medial hamstrings often provide dynamic support against valgus stress and instability, some surgeons feel that chronic or residual medial collateral ligament laxity (grade 2 or more) at the time of ACL reconstruction may be a contraindication for use of the patient’s own semitendinosus and gracilis tendons as an ACL graft.

Quadriceps tendon autograft

The quadriceps tendon autograft is often used for patients who have already failed ACL reconstruction. The middle third of the patient’s quadriceps tendon and a bone plug from the upper end of the knee cap are used. This yields a larger graft for taller and heavier patients. Because there is a bone plug on one side only, the fixation is not as solid as for the patellar tendon graft. There is a high association with postoperative anterior knee pain and a low risk of patella fracture. Patients may find the incision is not cosmetically appealing.

Allografts

Allografts are grafts taken from cadavers and are becoming increasingly popular. These grafts are also used for patients who have failed ACL reconstruction before and in surgery to repair or reconstruct more than one knee ligament. Advantages of using allograft tissue include elimination of pain caused by obtaining the graft from the patient, decreased surgery time and smaller incisions. The patellar tendon allograft allows for strong bony fixation in the tibial and femoral bone tunnels with screws.

However, allografts are associated with a risk of infection, including viral transmission (HIV and Hepatitis C), despite careful screening and processing. Several deaths linked to bacterial infection from allograft tissue (due to improper procurement and sterilization techniques) have led to improvements in allograft tissue testing and processing techniques. There have also been conflicting results in research studies as to whether allografts are slightly more susceptible to graft elongation (stretching), which may lead to increased laxity during testing.

Some published literature may point to a higher failure rate with the use of allografts for ACL reconstruction. Higher failure rates for allografts have been reported in young, active patients returning to high-demand sporting activities after ACL reconstruction, compared with autografts.

The reason for this higher failure rate is unclear. It could be due to graft material properties (sterilization processes used, graft donor age, storage of the graft). It could possibly be due to an ill-advised earlier return to sport by the athlete because of a faster perceived physiologic recovery, when the graft is not biologically ready to be loaded and stressed during sporting activities. Further research in this area is indicated and is ongoing.

Surgical Procedure

Before any surgical treatment, the patient is usually sent to physical therapy. Patients who have a stiff, swollen knee lacking full range of motion at the time of ACL surgery may have significant problems regaining motion after surgery. It usually takes three or more weeks from the time of injury to achieve full range of motion. It is also recommended that some ligament injuries be braced and allowed to heal prior to ACL surgery.

The patient, the surgeon, and the anesthesiologist select the anesthesia used for surgery. Patients may benefit from an anesthetic block of the nerves of the leg to decrease postoperative pain.

The surgery usually begins with an examination of the patient’s knee while the patient is relaxed due the effects of anesthesia. This final examination is used to verify that the ACL is torn and also to check for looseness of other knee ligaments that may need to be repaired during surgery or addressed postoperatively.

If the physical exam strongly suggests the ACL is torn, the selected tendon is harvested (for an autograft) or thawed (for an allograft) and the graft is prepared to the correct size for the patient.

After the graft has been prepared, the surgeon places an arthroscope into the joint. Small (one-centimeter) incisions called portals are made in the front of the knee to insert the arthroscope and instruments and the surgeon examines the condition of the knee. Meniscus and cartilage injuries are trimmed or repaired and the torn ACL stump is then removed.

In the most common ACL reconstruction technique, bone tunnels are drilled into the tibia and the femur to place the ACL graft in almost the same position as the torn ACL. A long needle is then passed through the tunnel of the tibia, up through the femoral tunnel, and then out through the skin of the thigh. The sutures of the graft are placed through the eye of the needle and the graft is pulled into position up through the tibial tunnel and then up into the femoral tunnel. The graft is held under tension as it is fixed in place using interference screws, spiked washers, posts, or staples. The devices used to hold the graft in place are generally not removed.

Variations on this surgical technique include the “two-incision,” “over-the-top,” and “double-bundle” types of ACL reconstructions, which may be used because of the preference of the surgeon or special circumstances (revision ACL reconstruction, open growth plates).

Before the surgery is complete, the surgeon will probe the graft to make sure it has good tension, verify that the knee has full range of motion and perform tests such as the Lachman’s test to assess graft stability. The skin is closed and dressings (and perhaps a postoperative brace and cold therapy device, depending on surgeon preference) are applied. The patient will usually go home on the same day of the surgery.

Surgical Complications

• Infection. The incidence of infection after arthroscopic ACL reconstruction is very low. There have also been reported deaths linked to bacterial infection from allograft tissue due to improper procurement and sterilization techniques.
• Viral transmission. Allografts specifically are associated with risk of viral transmission, including HIV and Hepatitis C, despite careful screening and processing. The chance of obtaining a bone allograft from an HIV-infected donor is calculated to be less than 1 in a million.
• Bleeding, numbness. Rare risks include bleeding from acute injury to the popliteal artery, and weakness or paralysis of the leg or foot. It is not uncommon to have numbness of the outer part of the upper leg next to the incision, which may be temporary or permanent.
• Blood clot. Although rare, blood clot in the veins of the calf or thigh is a potentially life-threatening complication. A blood clot may break off in the bloodstream and travel to the lungs, causing pulmonary embolism or to the brain, causing stroke.
• Instability. Recurrent instability due to rupture or stretching of the reconstructed ligament or poor surgical technique is possible.
• Stiffness. Knee stiffness or loss of motion has been reported by some patients after surgery.
• Extensor mechanism failure. Rupture of the patellar tendon (patellar tendon autograft) or patella fracture (patellar tendon or quadriceps tendon autografts) may occur due to weakening at the site of graft harvest.
• Growth plate injury. In young children or adolescents with ACL tears, early ACL reconstruction creates a possible risk of growth plate injury, leading to bone growth problems. The ACL surgery can be delayed until the child is closer to reaching skeletal maturity. Alternatively, the surgeon may be able to modify the technique of ACL reconstruction to decrease the risk of growth plate injury.
• Kneecap pain. Postoperative anterior knee pain is especially common after patellar tendon autograft ACL reconstruction. The incidence of pain behind the kneecap varies greatly in studies, whereas the incidence of kneeling pain is often higher after patellar tendon autograft ACL reconstruction.

Rehabilitation

Whether your treatment involves surgery or not, rehabilitation plays a vital role in getting you back to your daily activities. A physical therapy program will help you regain knee strength and motion.

If you have surgery, physical therapy with exercises beginning immediately after the surgery focuses on returning motion to the joint and surrounding muscles. This is followed by a strengthening program designed to protect the new ligament. This strengthening gradually increases the stress across the ligament. The final phase of rehabilitation is aimed at a functional return tailored for the athlete’s sport.

Much of the success of ACL reconstructive surgery depends on the patient’s dedication to rigorous physical therapy. With new surgical techniques and stronger graft fixation, current physical therapy uses an accelerated course of rehabilitation.

Postoperative Course. In the first 10 to 14 days after surgery, the wound is kept clean and dry, and early emphasis is placed on regaining the ability to fully straighten the knee and restore quadriceps control.

The knee is iced regularly to reduce swelling and pain. The surgeon may dictate the use of a postoperative brace and the use of a machine to move the knee through its range of motion. Weight-bearing status (use of crutches to keep some or all of the patient’s weight off of the surgical leg) is also determined by physician preference, as well as other injuries addressed at the time of surgery.

Rehabilitation. The goals for rehabilitation of ACL reconstruction include reducing knee swelling, maintaining mobility of the kneecap to prevent anterior knee pain problems, regaining full range of motion of the knee, as well as strengthening the quadriceps and hamstring muscles.

The patient may return to sports when there is no longer pain or swelling, when full knee range of motion has been achieved, and when muscle strength, endurance and functional use of the leg have been fully restored.

The patient’s sense of balance and control of the leg must also be restored through exercises designed to improve neuromuscular control. This usually takes 4 to 6 months. The use of a functional brace when returning to sports is ideally not needed after a successful ACL reconstruction, but some patients may feel a greater sense of security by wearing one.

ACL injury prognosis

Return to activity is variable and patient-dependent ²⁵. ACL injuries can be managed nonoperatively or surgically. The patient with an anterior cruciate ligament injury should be referred to the orthopedic surgeon to discuss treatment options and a physical therapist for rehabilitation.

Most partial tears can be treated with bracing and physical therapy (PT). A person might need to use crutches as the tear heals.

Some complete ACL tears need surgery. The need for surgery depends on many things, including:

• the type of the activities (or sports) the person wants to do
• if the person is an athlete
• age
• other injuries to the knee
• if the knee “gives way” or feels unstable

Your expectations for knee function or performance may play a role in determining whether ACL reconstruction is needed. With an ACL tear, your knee is usually unstable. This instability may cause your knee to “give way” or feel unstable which will significantly influence knee function. A course of physical therapy may successfully treat an ACL injury for people who are relatively inactive, engage in moderate exercise and recreational activities, or play sports that put less stress on the knees.

If physiotherapy and the possibly the use of a special ACL brace do not improve the stability of the joint, your doctor may recommend surgical reconstruction. Your Sports physician will also consider whether there are additional knee injuries which make surgery necessary, such as a meniscal tear and discuss fully your options of treatment.

Your doctor may recommend surgery if:

• You’re an athlete and want to continue in your sport, especially if the sport involves jumping, cutting or pivoting
• More than one ligament or the fibrous cartilage in your knee also is injured
• The injury is causing your knee to buckle during everyday activities

The average return to full activity and/or sports participation is estimated to be between 6 to 12 months after surgical reconstruction, depending upon their progress with physical therapist and the type of sport/activity to which they are returning. However, some studies have shown up to 18 months or more for the graft to become fully functional and incorporated. Early/premature return to activity can lead to re-injury and graft failure.

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